Many diverse medical conditions directly affect the lungs and overall pulmonary function. Accordingly, respiratory data can provide valuable information concerning the existence, onset and progression of a disease or injury affecting a patient. Several different methods are currently used to monitor pulmonary or respiratory functionality. Unfortunately, existing respiratory monitoring methods are complex, inconvenient, limited in scope or simply too expensive. None lend themselves to effective use in an ambulatory setting and instead, generally require that a subject be monitored in a hospital or doctor's office.
Consequently, delivery of a simple, reliable and portable apparatus to collect desired respiratory information would be invaluable to society and satisfy a long-felt need in the healthcare profession. The ability to safely, easily, and accurately measure respiratory function along with specific intermittent events and overall trends will provide the healthcare professional with critical information needed to provide appropriate and timely care. An apparatus that provides a reliable, simple means to measure and monitor respiratory function in conjunction with other physiological metrics, including heart rate, has been highly sought after. Additionally, the provision of such a device for use in an ambulatory setting would enable a health care provider to gain unique insight into a person's pulmonary responses to various stresses in a normal, everyday setting. This has been a long-felt need for decades which others have yet been unable to satisfy.
Both qualitative and quantitative aspects of respiratory function need to be monitored to assess, diagnose and treat problematic respiratory symptoms which may be driven by one of many respiratory, cardiac and other diseases. In particular, respiratory rate, rhythm, and, tidal volume are important parameters commonly measured to aid a physician in determining a patient's state of respiratory health and uncover other conditions that might affect respiratory health. It would be highly desirable to provide a respiratory monitoring apparatus that can easily be used by an individual or caregiver, regardless of the individual's current health status, mobility or lack thereof. In addition, it would be highly desirable to provide such an apparatus that can remain continuously with a patient during transition within a hospital setting and subsequently during outpatient treatment. Still further, it would be highly desirable to provide such an apparatus for nonintrusive use by an individual during normal daily routines to aid in the capture of respiratory events and trends which may be indicative of an adverse condition which might otherwise go unnoticed.
To understand the operation of the present invention and its utility and importance in providing assessment of respiratory function and performance, it will help to have a reasonable understanding of the various mechanical aspects of respiratory function along with the current methods used to measure important respiratory metrics. Following is a directed overview of relevant elements of respiratory function.
1. Related Art
An assessment of the mechanics of breathing deals with the movement of the diaphragm and associated muscles, movement of the rib-cage and associated musculature, and, physical characteristics of the lungs themselves. The muscular action controls breathing and it causes the volume of the lungs to increase and decrease in order to regulate the content of carbon dioxide in the arterial blood. Currently, there are various methods used to assess the function of each breathing mechanism component, however no single device is known that can easily, conveniently and accurately evaluate the overall performance of breathing. Existing methods used for respiratory assessment include: (1) the displacement method, which consists of wearing a chest wrap with adhesive sensors attached to it, (2) the thermistor method, which requires a facial mask for measuring respiration heat, (3) the impedance pneumography test, which attaches electrodes on the surface of the skin and measures chest movement, (4) the CO2 method, which consists of a continuous measurement of expired air and the utilization of infrared rays, and, (5) a piezoelectric external mechanical movement detection and correlation method. It is important to note that all of the above approaches fail to obtain direct information concerning the both the mechanical aspects of the respiratory process and the physiological changes within the lungs themselves during the respiratory process.
Certain elements of respiration may be measured directly using, for example, external breathing masks. Breathing masks, however, are generally not well tolerated by patients for extended periods of time. Additionally, such masks are not convenient for ambulatory patients. Additionally, a system having one or more sensors disposed at or near the surface of a patient's body for monitoring physiological variables of a patient in real time, including respiratory sounds for the detection of abnormal breathing patterns, is generally disclosed in U.S. Pat. No. 5,738,102 issued to Lemelson.
Further, qualitative assessments of respiratory function are made via impedance measurements using implanted electrodes for detecting changes in thoracic impedance associated with changing lung volume during inspiration and expiration. Tidal volume and respiration rate may be approximated from the measured impedance. Normal changes in respiration rate and tidal volume in response to exercise are measured using impedance sensing in some cardiac pacemakers to provide a sensor-indicated pacing rate for rate-responsive cardiac pacing. See, for example, U.S. Pat. No. 4,901,725 issued to Nappholz.
Still further, respiratory signals may be extracted from other physiological signals that can be obtained from implantable sensors. For example, physiological signals, such as subcutaneous ECG, cardiac electrogram (EGM), blood pressure, and heart sound signals, typically contain cyclical amplitude changes caused by the respiratory cycle. Pulsus paradoxus refers to a decrease in arterial blood pressure that occurs during inspiration. A device for measuring pulsus paradoxus for assessing and monitoring patients with respiratory disease is generally disclosed in U.S. Pat. No. 6,325,761 issued to Jay, incorporated herein by reference in its entirety. A method for computing tidal volume as a function of extracted blood pressure information indicative of the change in blood pressure that occurs over a respiratory cycle is generally disclosed in U.S. Pat. No. 5,980,463, issued to Brockway, et al. Implantable cardiac rhythm management or cardiac monitoring devices may sense ECG, EGM, blood pressure and/or other physiological signals that vary due to the influence of respiration.
Each of the above existing methods is relatively complex, expensive and somewhat invasive. They do not lend themselves to use outside a hospital or doctor's office. It would be advantageous and beneficial to provide an apparatus capable of monitoring the desired parameters more simply and noninvasively, in a manner that allows continuous use in essentially any location.
2. Respiratory Metrics
Monitoring and assessment of lung function is an indispensable tool for diagnosing and monitoring respiratory disease states, along with the root causes of the current respiratory state or other diseases associated with the respiratory state. There are several key respiratory functional metrics that are considered when assessing an individual's respiratory health. FIG. 1 is a chart illustrating the relationship between the various standard metrics. A first metric is an individual's total lung capacity, which is a cumulative measure of the additional metrics of inspiratory reserve volume, including tidal volume, expiratory reserve volume, and residual volume. Inspiratory reserve volume is the additional air that can be inhaled after a normal tidal breath in. Tidal volume is the normal volume of air breathed in and out. Expiratory reserve volume is the amount of additional air that can be breathed out after the end expiratory level of normal breathing. Residual volume is the amount of air left in the lungs after a maximal exhalation, i.e., the amount of air that is always in the lungs and can never be expired.
Measuring an individual's total lung capacity can provide critical background information about a person, and, needs to be considered in making diagnoses. An individual's total lung capacity typically depends on such factors as the person's age, height, weight, and sex. Total lung capacity normally ranges between 4 to 6 liters. Females tend to have a 20-25% lower total lung capacity than males. Tall people tend to have a larger total lung capacity than shorter people. Smokers tend to have a lower total lung capacity than nonsmokers. Lung capacity can also be affected by altitude. People who are born and live at sea level will typically have a smaller lung capacity than people who spend their lives at a high altitude.
In addition to measuring total lung capacity, one also measures tidal volume, the volume of air breathed in with an average breath. Tidal volume is typically between 0.5 to 1 liters. Measurement of tidal volume and changes or trends in tidal volume provides critical diagnostic data concerning pulmonary function and performance. For example, typical resting adult respiratory rates are 10 to 20 breaths per minute with approximately a third of the breath time involved in inspiration. Human lungs, to a certain extent, are overbuilt and have a tremendous reserve volume as compared to the normal oxygen exchange requirements when an individual is at rest. For example, individuals can smoke for years without having a noticeable decrease in lung function while still or moving slowly. For example, although total lung capacity may be between 4 to 6 liters, with tidal volume between 0.5 to 1 liters, only a small portion of the total lung capacity is typically in use, approximately between 8% to a maximum of 25%. While in a resting state, only a small portion of the lungs are actually perfused with blood for gas exchange. As oxygen requirements increase due to exercise, a greater volume of the lungs is perfused, allowing the body to reach its CO2/O2 exchange requirements. Hence, the smoker engaged in exercise will most likely experience an oxygen deficit due to existing damage to the lungs which prevents perfusion of a greater volume of the lung area.
It would be advantageous to provide a convenient, small apparatus and sensor capable of both qualitatively and quantitatively measuring the various pulmonary functional parameters including respiratory rate, respiratory rhythm, tidal volume, and, total lung capacity, along with other calculable and derivative parameters such as vital capacity and residual volume, among others. It would also be advantageous to provide such an apparatus capable of measuring changes in perfusion in each lobe of one or both lungs.
3. Respiratory Metrics of Primary Respiratory Diseases
Respiratory diseases can generally be categorized as obstructive, restrictive, parenchymal, vascular or infectious. Following is a brief overview of these respiratory disease types relevant to the application of the present invention.
Obstructive lung diseases (OLD) are characterized by an increase in airway resistance, evidenced by a decrease in Peak Expiratory Flow Rate (PEFR) measured in spirometry by the Forced Expiratory Volume in 1 Second (FEV1). The Residual Volume, the volume of air left in the lungs following full expiration, is greatly increased in OLD, leading to the clinical sign of chest over-inflation in patients with severe disease. Many patients with chronic OLD present with “barrel chest”—a deformity of outward rib displacement due to chronic over-inflation of the lungs. Patients with OLD typically have ‘large, floppy lungs’. In Obstructive Lung Disease, the lung volume (Total Lung Capacity, TLC), Vital Capacity (VC), Tidal Volume (VT) and Expiratory Reserve Volume (ERV) remain relatively unchanged. It would be advantageous to provide a simple, noninvasive apparatus and sensor that could monitor and track chest over-inflation and lung size in conjunction with the other functional pulmonary metrics to assess the onset and progression of OLD in patients in a continuous manner. Some notable obstructive lung diseases which could be more competently assessed through the provision and use of such an apparatus and sensor include emphysema, bronchitis, asthma, chronic obstructive pulmonary disease, bronchiectasis, byssinosis, bronchiolitis, and, asbestosis.
Restrictive lung diseases (RLD) are characterized by a loss of airway compliance, causing incomplete lung expansion (i.e. via increased lung ‘stiffness’). This change manifests itself in reduced Total Lung Capacity, Inspiratory Capacity and Vital Capacity. In contrast to OLD, RLD values for Tidal Volume, Expiratory Reserve Volume, Functional Residual Capacity and Respiratory Volume are unchanged. It would be advantageous to provide a simple, noninvasive apparatus and sensor that could monitor and track changes in total lung capacity, inspiratory capacity and vital capacity along with other pulmonary metrics to assess the onset and progression of RLD in patients in a continuous manner. Notable restrictive lung diseases which could be more competently assessed through the provision and use of such an apparatus and sensor include fibrosis, sarcoidosis, pleural effusion, hypersensitivity pneumonitis, asbestosis, pleurisy, lung cancer, infant respiratory distress syndrome (IRDS), acute respiratory distress syndrome (ARDS), neurologic diseases affecting the ability of the body to alter respiration rate including spinal cord injury, mechanical diseases affecting pulmonary musculature including myasthenia gravis, and, severe acute respiratory syndrome (SARS).
Parenchymal lung disease is characterized by damage to the lungs which may be caused by environmental or other factors. The basic functional units of the lung, the alveoli, are referred to as the lung parenchyma. Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive airway disease (COAD), is a group of diseases characterized by the pathological limitation of airflow in the airway that is not fully reversible. COPD is the umbrella term for chronic bronchitis, emphysema and a range of other lung disorders. It is most often due to tobacco smoking, but can be due to other airborne irritants such as coal dust, asbestos or solvents, as well as congenital conditions. Diseases such as COPD are characterized by destruction of the alveoli and are therefore referred to as parenchymal lung diseases. Signs of parenchymal lung disease include, but are not limited to, hypoxemia (low oxygen in the blood) and hypercapnoea (high carbon dioxide in the blood). In addition, parenchymal lung diseases can present with symptoms of elevated respiratory rate with corresponding reduced tidal volume. Chronic complications of parenchymal lung disease include reduced respiratory drive, right ventricular hypertrophy, and right heart failure (cor pulmonale). Notable parenchymal diseases include COPD, sarcoidosis, pulmonary fibrosis, and, emphysema. It would be advantageous to provide a simple, noninvasive apparatus and sensor that could continuously and directly monitor respiratory rate in correspondence with changes in tidal volume in conjunction with the other functional pulmonary metrics to assess the onset and progression of parenchymal lung diseases in patients.
Vascular lung disease refers to conditions which affect the pulmonary capillary vasculature. Alterations in the vasculature manifest in a general inability to exchange blood gases such as oxygen and carbon dioxide, in the vicinity of the vascular damage (other areas of the lung may be unaffected). Signs of vascular lung disease include, but are not limited to, hypoxemia (low oxygen in the blood) and hypercapnoea (high carbon dioxide in the blood). Chronic complications of vascular lung disease include reduced respiratory drive, right ventricular hypertrophy, and right heart failure (cor pulmonale). In addition, parenchymal lung diseases can present with symptoms of elevated respiratory rate with corresponding reduced tidal volume. For example, pulmonary hypertension, a vascular lung disease, is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion. Notable vascular lung diseases include pulmonary edema, pulmonary embolism, and, pulmonary hypertension. It would be advantageous to provide a simple, noninvasive apparatus and sensor that could continuously and directly monitor respiratory rate indicating breathlessness and tidal volume in conjunction with the other functional pulmonary metrics to assess the onset and progression of vascular lung diseases in patients.
Infectious lung diseases are typically caused by one of many infectious agents able to infect the mammalian respiratory system, for example, the bacterium Streptococcus pneumoniae. The clinical features and treatment options vary greatly between infectious lung disease sub-types as each type may be caused by a different infectious agent, with different pathogenesis and virulence. Features also vary between upper respiratory tract infection, including strep throat and the common cold; and lower respiratory tract infection, including pneumonia and pulmonary tuberculosis. Lower respiratory tract infections place a considerable strain on the health budget and are generally more serious than upper respiratory infections. Since 1993 there has been a slight reduction in the total number of deaths from lower respiratory tract infection. However in 2002 they were still the leading cause of deaths among all infectious diseases accounting for 3.9 million deaths worldwide and 6.9% of all deaths that year.
These infectious lung diseases typically present with symptoms of shortened breath resulting in a corresponding increase in respiratory rate. It would be advantageous to provide a simple, noninvasive apparatus and sensor that could continuously and directly monitor respiratory rate and tidal volume in conjunction with the other functional pulmonary metrics to assess the onset and progression of infectious lung disease in patients.
Respiratory tumor can refer to either neoplastic (cancerous) or non-neoplastic masses within the lungs or lung parenchyma. Respiratory neoplasms are abnormal masses of tissue within the lungs or parenchyma whose cell of origin may or may not be lung tissue (many other neoplasms commonly metastasize to lung tissue). Respiratory neoplasms are most often malignant, although there are non-malignant neoplasms which can affect lung tissue. Respiratory neoplasms include mesothelioma, small cell lung cancer, and, non-small cell lung cancer. Each of these typically present with symptoms of shortness of breath. Consequently, it would be advantageous to provide a simple, noninvasive apparatus and sensor that could continuously and directly monitor respiratory rate and tidal volume thereby assessing shortness of breath, in conjunction with the other functional pulmonary metrics, to allow assessment of the onset and progression of infectious lung diseases in patients.
4. Respiratory Metrics and Indicators of Cardiac Failure
Measurement of pulmonary functionality and performance can be a tremendous aid in identifying symptoms associated with cardiac problems. For example, congestive heart failure (CHF) is a condition that can result from any structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood through the body. Congestive heart failure is often undiagnosed due to a lack of a universally agreed definition and difficulties in diagnosis, particularly when the condition is considered “mild”. Even with the best therapy, heart failure is associated with an annual mortality of 10% (Stefan Neubauer (2007). “The failing heart—an engine out of fuel”. N Engl J Med 356 (11): 1140-51). It is the leading cause of hospitalization in people older than 65. (McKee P A, Castelli W P, McNamara P M, Kannel W B (1971). “The natural history of congestive heart failure: the Framingham study”. N. Engl. J. Med. 285 (26): 1441-6.)
The symptoms of congestive heart failure depend largely on the side of the heart exhibiting predominant failure. If both sides are functioning inadequately, symptoms and signs from both categories may be present. Given that the left side of the heart pumps blood from the lungs to the organs, failure to do so leads to congestion of the lung veins and symptoms that reflect this, as well as reduced supply of blood to the tissues. The predominant respiratory symptom is shortness of breath on exertion, dyspnea (or, in severe cases at rest) along with becoming easily fatigued. Orthopnea is increasing breathlessness on reclining, measured in the number of pillows required to lie comfortably. Paroxysmal nocturnal dyspnea (PND) is a nighttime attack of severe breathlessness, usually several hours after going to sleep. Poor circulation to the body leads to dizziness, confusion and diaphoresis (excessive sweating) and cool extremities at rest. It is most closely associated with congestive heart failure. PND is often relieved by sitting upright, but not as quickly as simple orthopnea. Also unlike orthopnea, it does not develop immediately upon laying down. Consequently, it would be highly advantageous to provide a non-invasive, convenient sensor that could be comfortably worn by an individual to assist in the identification of changes in respiratory rate and rhythm that may suggest the onset of congestive heart failure, when an individual is active, recumbent or asleep.
Paroxysmal nocturnal dyspnea (PND) is caused by increasing amounts of fluid entering the lung during sleep and filling the small, air-filled sacs in the lung, the alveoli, which are responsible for absorbing oxygen from the atmosphere for exchange with blood. This fluid typically rests in the legs (peripheral edema), causing swelling in the leg tissues during the day when the individual is upright. At night, when recumbent for an extended period, this fluid is reabsorbed, increasing total blood volume and blood pressure, leading to pulmonary hypertension (high blood pressure) in people with underlying left ventricular dysfunction. The pulmonary hypertension leads to the accumulation of fluid in the lungs, or pulmonary edema. Pulmonary edema is swelling and/or fluid accumulation in the lungs. It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the heart to remove fluid from the lung circulation (“cardiogenic pulmonary edema”), or due to a direct injury to the lung parenchyma (“noncardiogenic pulmonary edema”). Treatment depends on the cause, but focuses on maximizing respiratory function and removing the cause. It would be highly advantageous to provide a non-invasive, convenient apparatus and sensor that could be comfortably worn by an individual to assist in the identification of changes in fluid in the lungs and alveoli that may suggest the onset of congestive heart failure, when an individual is active, recumbent or asleep.
The right side of the heart pumps blood returned from the tissues to the lungs to exchange CO2 for O2. Hence, failure of the right side leads to congestion of peripheral tissues. This may lead to peripheral edema or anasarca and nocturia (frequent nighttime urination when the fluid from the legs is returned to the bloodstream). Anasarca (“extreme generalized edema”) is a medical symptom characterized by widespread swelling of the skin due to effusion of fluid into the extracellular space. In more severe cases, ascites (fluid accumulation in the abdominal cavity) and hepatomegaly (painful enlargement of the liver) may develop.
Heart failure may decompensate easily; this may occur as the result of any intercurrent illness (such as pneumonia), but specifically myocardial infarction (a heart attack), anemia, hyperthyroidism or arrhythmias. These place additional strain on the heart muscle, which may cause symptoms to rapidly worsen. Excessive fluid or salt intake (including intravenous fluids for unrelated indications) and medication that causes fluid retention (such as NSAIDs and thiazolidinediones) may also precipitate decompensation.
5. Respiratory Metrics and Indicators of Other Pathological Conditions
Respiratory events or disturbances may be associated with a number of pathological conditions. Various respiratory metrics will provide indicators of these pathological conditions. For example, Cheyne-Stokes respiration is the waxing and waning of respiration associated with congestive heart failure. Kussmaul breathing is rapid deep breathing associated with diabetic ketoacidosis. Central or obstructive forms of sleep apnea are prevalent in both normal and heart failure populations. Detection of those respiratory events may be useful in monitoring a patient's disease status, selecting treatment and monitoring its effectiveness. It would be highly advantageous to provide a non-invasive, convenient apparatus and sensor that could be comfortably worn by an individual to assist in the identification of these respiratory events or disturbances when an individual is active, ambulatory, recumbent or asleep.
Sleep apnea is a typically chronic condition that can serve as the catalyst for several different pathological conditions. Respiratory disturbances in the form of sleep-related disordered breathing may often go undetected in patients suffering from heart failure or sleep apnea. Nocturnal Cheyne-Stokes respiration, a form of central sleep apnea, occurs frequently in patients with chronic heart failure. The presence of sleep apnea significantly worsens the prognosis for a heart failure patient. A method for determining the cardiac condition of a patient by a cardiac monitor using the variability of a respiration parameter is generally disclosed in U.S. Pat. No. 6,454,719 issued to Greenhut, incorporated herein by reference in its entirety. Characteristics of periodic breathing patterns, such as hyperpnea length, apnea length, and periodic breathing cycle length, are correlated to circulatory delay time, which is inversely correlated with cardiac output. Therefore, recognizing and monitoring the presence of disordered breathing in heart failure patients could provide useful diagnostic and prognostic information. Moreover, detecting respiratory disturbances and extracting specific parameters related to cardiac function could provide valuable information for assessing a patient's cardiac condition and optimizing therapeutic interventions. Consequently, it would be highly beneficial to provide a simple apparatus and sensor capable of noninvasively monitoring respiratory rate, rhythm and periodic events to identify and diagnose conditions during a person's sleep which might be indicative of cardiac complications or disturbances, particularly sleep apnea.
A standard approach for diagnosis of sleep apnea includes polysomnography, which requires the patient to stay overnight in a hospital for observation, in addition to medical history and screening questionnaires. Polysomnography involves monitoring of multiple parameters including electroencephalography, electromyography, electrocardiography, oximetry, airflow, respiratory effort, snoring, body position and blood pressure.
Polysomnography or a controlled sleep study, which can be used to identify sleep apnea, measures a patient's respiratory patterns during a single sleeping period. However, this procedure is expensive and inconvenient for the patient. Furthermore, a physician must actively prescribe the sleep study and therefore must already suspect a sleep-related breathing disorder. Chronic monitoring of respiratory disturbances as an alternative to polysomnography, particularly in heart failure patients who have increased risk of morbidity in the presence of sleep apnea, is desirable for detecting unrecognized and unsuspected sleep-related disordered breathing. Providing a single, simple apparatus and sensor capable of monitoring the majority of these parameters without having to resort to a complex configuration of sensors and without requiring an overnight stay at a hospital would be highly beneficial to patients and would increase the ability of healthcare providers to more readily identify those persons actually suffering from sleep apnea by collecting the necessary data in their own home setting while sleeping in their own bed, while also substantially reducing the costs associated with this diagnosis.
Diabetes is another disease which may be assessed via effective monitoring of respiratory metrics. Diabetic patients can also benefit from continuous monitoring of their pulmonary functionality and performance. For example, diabetic ketoacidosis may be the first symptom to appear in a person with Type I diabetes. Diabetic ketoacidosis develops when blood is more acidic than body tissues due to the accumulation of ketones in the blood when body fat is metabolized for energy in place of glucose reserves when insulin is not available. Persons having Type II diabetes usually develop ketoacidosis only under conditions of severe stress. Recurrent episodes of ketoacidosis in diabetic persons are generally the result of poor compliance with dietary restrictions or self-administered treatments. Kussmaul breathing, characterized by relatively deep breathing, is a common symptom of ketoacidosis. Therefore early detection and monitoring of Kussmaul breathing in diabetic patients may be valuable in the effective control of diabetes. Consequently, providing diabetic patients with a simple, easy-to-use, non-invasive respiratory apparatus and sensor in addition to devices to measure blood glucose may prove highly beneficial in allowing diabetic patients to more adequately control their diabetic conditions to minimize negative symptoms and effects.
Heart failure and lung failure frequently go hand-in-hand, and hence, this condition can be assessed via effective respiratory monitoring. As previously indicated, heart failure typically presents with symptoms of shortness of breath or elevated respiration rate, among other things. Consequently, it would be extremely beneficial to provide persons with a simple, noninvasive apparatus and sensor that could continuously and directly monitor respiratory rate and rhythm in conjunction with the other functional pulmonary metrics to assess the onset and progression of potential congestive heart failure in patients. In particular, it would be extremely advantageous to provide such a device for elderly patients most susceptible to congestive heart failure. Further, it would be highly advantageous to provide such a device for use by persons who have undergone cardiac surgery to continuously monitor respiratory rate and rhythm to provide tangible evidence to the patient that the surgery was successful, thereby reducing anxiety concerning future potential heart failure. It would be still further advantageous to provide such a device that can simultaneously monitor both cardiac and pulmonary rate and rhythm to provide a more meaningful assessment and correlation between changes in either cardiac or pulmonary functionality.
In light of the plethora of pulmonary diseases which may be more competently assessed via the use of an effective respiratory measurement device, and, given the correlation between respiratory function and cardiac health, it would be highly desirable to provide a wearable device that can detect advanced respiratory functions, is non-invasive, does not require surgery for implantation, does not require skin contact, conductive gels or electrode patches, does not require wearing an uncomfortable band wrapped around the chest, is low power without any ionizing radiation, allows long-term continuous patient monitoring in both hospital and ambulatory settings, is safe, allows real-time 24/7 monitoring, and is more affordable than current techniques and devices. It would be further highly desirable to provide such a device capable of simultaneously monitoring both cardiac and respiratory functionality. The present invention is directed to providing the above desired features which have been long sought after by healthcare providers.